Overhauled ApacheBench (ab) manpage ab.8.

Submitted by: Simon Baldwin <simonb@sco.com>
Reviewed by: Ralf S. Engelschall
PR: 5139


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@84045 13f79535-47bb-0310-9956-ffa450edef68